System for permanent electrode placement utilizing microelectrode recording methods

ABSTRACT

A lead stimulation/recording system is provided, which is a combination of a permanent DBS stimulating lead and a recording microelectrode. The DBS lead has a lumen extending from the proximal to the distal end of the lead, the lumen having an opening on each end of the lead. The microelectrode is configured and dimensioned to be insertable into the DBS lead from either the distal or proximal opening of the DBS lead, thereby permitting the microelectrode to be placed before, concurrently with, or after placement of the DBS lead. In addition, the system may be used with known microelectrode recording systems and methods of inserting the electrodes, such as the five-at-a-time method, the dual-microdrive method, or the single microdrive method.

The present application is a Continuation of application Ser. No.11/670,598, filed Feb. 2, 2007, which application is a Continuation ofapplication Ser. No. 10/459,068, filed Jun. 11, 2003, issued as U.S.Pat. No. 7,177,701 on Feb. 13, 2007; which application is aContinuation-In-Part of U.S. patent application Ser. No. 10/035,745,filed Dec. 28, 2001, issued as U.S. Pat. No. 7,033,326 on Apr. 25, 2006;which application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/258,767, filed Dec. 29, 2000, which applicationsand patents are incorporated by reference.

In addition, application Ser. No. 10/459,068 claims the benefit of U.S.Provisional Patent Application Ser. No. 60/388,871, filed Jun. 13, 2002,which application is also incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to medical leads and microelectroderecording systems used for functional neurosurgical procedures.

Deep brain stimulation (DBS) is being increasingly accepted as a viabletreatment modality. In particular DBS applied to the thalamus fortreatment of tremor was approved by the FDA in 1997. Subsequently, otherdiseases, such as Parkinson's Disease, dystonia, and chronic pain, amongothers, have been identified as candidates for treatment with deep brainstimulation.

The term “stylet,” as used in this disclosure, is an implement insertedinto the lumen of a stimulating lead to stiffen the lead and tofacilitate its insertion into the target tissue. The term “rod,” as usedin this disclosure, is an implement that is placed inside a cannula toprovide support to the cannula, while it is inserted into target tissue.The term “microelectrode” refers to a recording electrode which can beessentially a wire which has at least the distal portion of the wireuninsulated to receive electrical signals from the recorded tissue. Theterm “macroelectrode” will refer to a stimulating electrode and partsconnected to the electrode, which macroelectrode is intended as atemporary test electrode to perform macrostimulation. Macrostimulationinvolves stimulating many cells at once. The term “lead,” as usedhereinafter, will specifically refer only to a chronically implantablestimulation electrode, including parts connected to the electrode. Theelectrode portion of the lead is that portion which is in electricalcontact with tissue. The term “tract” refers to an individual pathwayformed in tissue, for example, by inserting a microelectrode, amacroelectrode, a lead or an associated cannula into that tissue.

Implantation of a lead for deep brain stimulation generally involves thefollowing preliminary steps: (a) anatomical mapping and (b)physiological mapping. Anatomical mapping involves mapping segments ofan individual's brain anatomy using non-invasive imaging techniques suchas magnetic resonance imaging (MRI) and computed axial tomography (CAT)scans. Physiological mapping involves localizing the brain site to bestimulated. Step (b) can be further divided into: (i) preliminarilyidentifying a promising brain site by recording individual cell activitywith a microelectrode and (ii) confirming physiological stimulationefficacy of that site by performing a test stimulation with amacroelectrode.

Microelectrode recording is generally performed with a small diameterelectrode with a relatively small surface area optimal for recordingcell activity. The microelectrode may be essentially a wire which has atleast the distal portion uninsulated to receive electrical signals. Therest of the body or wire of the microelectrode may be insulated. Themicroelectrode functions as a probe to locate a promising brain site.Since a number of attempts may be required to locate the precise targetsite, it is desirable that the microelectrode be as small as possible tominimize trauma when the microelectrode is placed into the brain, insome cases, multiple times.

Once a brain site has been identified, a macroelectrode is used to testthat the applied stimulation has the intended therapeutic effect. Amacroelectrode is a temporary stimulating electrode and is not intendedto be chronically implanted. Because macrostimulation involvesstimulating many cells at once, an optimal electrode formacrostimulation requires a larger surface area compared to amicroelectrode, which merely records electrical activity from a singlecell or a few cells. For this reason, the conductive electrode surfaceof a macroelectrode is generally larger than the conductive electrodesurface of a microelectrode. The macroelectrode can be retraced into thesame brain site identified with microelectrode cell recordings.

Test stimulation with the macroelectrode may need to be performed in anumber of tracts in order to localize the site which provides the properphysiological effect. Because the macroelectrode may need to berepeatedly inserted into the brain, the macroelectrode must be durable,stiff and resistant to buckling. The macroelectrode can be made from asterilizable material.

Once macrostimulation confirms that stimulation at the brain siteprovides the intended physiological effect, the macroelectrode iswithdrawn from the brain and a DBS lead is permanently implanted at theexact site.

Keeping in mind the above general steps, a conventional procedure forcarrying out DBS may involve the following detailed steps: (1) place astereotactic frame on the subject, which stereotactic frame is a devicetemporarily mounted on the head to assist in guiding the lead systeminto the brain; (2) perform MRI or equivalent imaging of the subjectwith the stereotactic frame; (3) identify a theoretical target using aplanning software; (4) place the subject with the stereotactic frame ina head rest; (5) using scalp clips, cut the subject's skin flap in thehead, exposing the working surface area of the cranium; (6) place thestereotactic arc with target coordinate settings and identify thelocation on skull for creation of a burr hole; (7) remove the arc anddrill a burr hole in the patient's skull; (8) place the base of the leadanchor; and (9) with the microelectrode recording drive attached, andwith an appropriate stereotactic frame adaptor inserted into theinstrument guide, place the stereotactic arc.

Next, (10) advance a microelectrode cannula and an insertion rod intothe brain until they are approximately 25 mm above the target; (11)remove the insertion rod, leaving the cannula in place; (12) insert arecording microelectrode such that the tip of the microelectrode isflush with the tip of the microelectrode cannula; (13) connect theconnector pin of the recording microelectrode to a microelectroderecording system; (14) starting approximately 25 mm above the target,advance the microelectrode into a recording tract at the specified rateusing the microdrive; and (15) if the target is identified, proceed tostep 16. If the target is not identified, proceed with the following:(17) using the recording results and pre-operative imaging, (a)determine a new set of coordinates for the theoretical target; (b)disconnect the recording microelectrode from the microelectroderecording system; (c) remove the recording microelectrode cannula andrecording microelectrode; and (d) adjust the coordinates of thestereotactic frame. Then, continue at step 10, above.

Next, (16) remove the recording microelectrode cannula and recordingmicroelectrode; (17) insert a macroelectrode insertion cannula and roduntil they are approximately 25 mm above the target; (18) remove theinsertion rod, leaving the macroelectrode insertion cannula in place;(19) insert a stimulating macroelectrode, and advance it to the targetstimulation site identified by the recording microelectrode; (20) usingmacrostimulation, simulate the stimulation of the chronic DBS lead toensure proper physiological response; (21) remove the macroelectrode andcannula; (22) insert a DBS lead insertion cannula and an insertion rod,and advance both to approximately 25 mm above the stimulation site; (23)remove the insertion rod; (24) insert a DBS lead, with stylet, throughthe insertion cannula, and advance the lead/stylet to the stimulationsite; (25) electrically connect the lead to a trial stimulator; and (26)perform the desired stimulation and measurements using any one orcombination of four electrodes on the DBS lead.

Next, (27) if the results are favorable, proceed to step 28. If theresults are not favorable, proceed with the following: (a) using themacrostimulation results and microelectrode recording results, as wellas pre-operative imaging, determine a new set of coordinates for thetheoretical target; (b) remove the lead and stylet; (c) remove theinsertion cannula; (d) adjust the coordinates of the stereotactic frame;and (e) continue at step 10, above.

Next, (28) remove the stylet, followed by the insertion cannula; (29)using macrostimulation, verify that micro-dislodgement of the DBS leadhas not occurred; and, finally, (30) lock the DBS lead in the leadanchor.

Some physicians might use additional steps, fewer steps, or perform thesteps in a different order.

There are a number of commercially available microelectrode recording(“MER”) systems used for deep brain stimulation. Such a system includesapparatuses for holding the microelectrodes in place and electronicsthat connect to the microelectrodes to enable cell recordings. MERsystems are sold by Alpha Omega Engineering (Nazareth, Israel), Axon(Union City, Calif.), Atlanta Research Group (Atlanta, Ga.), andMicrorecording Consultants (Pasadena, Calif.). The Alpha Omega and Axonsystems appear to be among the most popular with functionalneurosurgeons. None of these companies manufacture their ownmicroelectrodes, although they may provide a microelectrode as part ofthe MER system package. The Fred Haer Corporation (FHC) markets apopular microelectrode which is sometimes provided in the MER systempackage.

The Alpha Omega Engineering MER system permits the neurosurgeon tosimultaneously record “five-electrodes-at-a-time” recordings. In thisapproach all five of the microelectrodes are advanced into the brain atthe same time and at the same speed. This presents obvious advantages.The set-up time may be proportionately cut, since the chance of locatinga good stimulation site theoretically increases by five times. Adisadvantage presented is that because the microelectrodes are placedrelatively close to each other, two of these electrodes could “capture”a blood vessel between the electrodes, puncturing the vessel andpossibly leading to intracranial bleeding. In contrast, when a singlemicroelectrode is used, the blood vessel can often escape injury becausethe vessel can deflect away from the microelectrode or vice-versa. Thus,some neurosurgeons choose to use the Alpha Omega MER system with only asingle microdrive, advancing one microelectrode at a time until asuitable placement site is found. Other neurosurgeons have used theAlpha Omega system with two independent microdrives, which provides theflexibility of recording independently from two tracts.

Other neurosurgeons use the Axon system, which can manually advance onlyone microelectrode at time. Some neurosurgeons average 4 to 5microelectrode recording tracts to identify a suitable brain site. Otherneurosurgeons only record from one recording tract, which cuts surgeryduration, but which may not locate an optimal stimulation site. Withoutoptimal electrode placement, the DBS lead may need to be stimulated athigher currents, which can cause the device battery to be drained morequickly. In addition, use of higher currents can increase the risk ofundesirable side effects such as dysarthria (slurred speech) and abulia(an abnormal inability to make decisions or to act).

Each of these MER systems apply the conventional surgical procedure ofusing the microelectrode to find the target brain site, withdrawing themicroelectrode, then placing a macroelectrode, followed by placing a DBSlead or alternatively, placing a DBS lead directly without using amacroelectrode. These conventional surgical procedures are far fromideal. The number of steps lengthen the surgical procedure and increasethe risk for post-operative infection. In addition, having to retracethe microelectrode pathway and the macroelectrode pathway to place theDBS lead substantially increases the chances for misalignment andmisplacement because each of these steps require use of a separateintroduction cannula. Moreover, the use of at least three cannulas inthe procedure can increase surgical duration and operative risk, simplyfrom the number of objects inserted into the brain. In addition,retracing the pathway of the microelectrode and the macroelectrode aspreliminary steps to placing the permanent DBS lead is fraught withmisalignment/misplacement problems because the introduction cannulas maynot trace the exact pathways desired. When there is a missed placementof a DBS lead, the DBS lead and stylet may have to be scrapped.

Accordingly, there is a need for a DBS lead/microelectrode system whichis compatible with the available MER systems and the various methods ofemploying these recording systems, which DBS lead/microelectrode systemeliminates surgical steps and reduces surgical duration, reducesoperative risk, and improves the accuracy of placing the permanentstimulation DBS lead to provide optimal physiological therapy.

SUMMARY OF THE INVENTION

The present invention addresses the above and other needs by providing aDBS lead/microelectrode system which is compatible with available MERsystems and a wide variety of recording techniques currently used byneurosurgeons, including “five-at-a-time,” two independent microdrives,and single tract, multiple insertion methods.

In one aspect of the present invention, a system for recording andstimulating excitable tissue is provided comprising a stimulation leadand a microelectrode. The stimulating lead may have a lumen along itsaxial length. The lumen has two openings, a first opening at theproximal end of the lead and a second opening at the distal end of thelead. The microelectrode is configured and dimensioned to be completelypassable through the lumen of the lead, commencing from either the firstopening or the second opening of the lead.

In another embodiment, the system may comprise: a stimulating lead, amicroelectrode, and a removable connector which can be attached anddetached to the proximal end of the microelectrode. The microelectrodeis configured and dimensioned to be completely passable through thelumen of the stimulating lead, commencing from either a first opening ora second opening of the stimulating lead.

In yet another embodiment, the above system may further include alocking mechanism incorporated into the connector. The locking mechanismon the connector may be a threaded connection, a clip connection, a setscrew connection, a spring-loaded connection, a ball bearing connection,a Bal Seal connection, a collet connection or an interference fit.

In each system embodiment, the stimulation lead may contain a conductorcoil that defines an inner, axial lumen. The stimulation lead may have,at its proximal end, a connector portion that is angled from theremainder of the lead. This connector angle helps to divert the leadconnection away from the remainder of the lead and prevents tanglingwith the microelectrode. The stimulation lead may have an array ofelectrodes placed on the distal portion of the lead in an in-lineplacement.

In another aspect of the invention, there is provided a method ofplacing a DBS stimulating lead and inserting a microelectrode thateliminates procedural steps and thus reduces critical operating time.Each embodiment of the method commonly shares the feature that themicroelectrode may be inserted and fully passed through the lumen of thestimulating lead, commencing at the lead's distal or proximal end. Theembodiments of the method include: (1) placing the microelectrode intotissue first and placing the DBS stimulating lead over themicroelectrode, (2) concurrently placing the microelectrode/DBSstimulating lead into a target tissue, or (3) placing the DBSstimulating lead into the target tissue first and then inserting themicroelectrode into the lumen of the DBS stimulating lead. Theflexibility of the various method embodiments can increase the accuracyof placing a DBS lead and microelectrode near the target neurons andthereby improve treatment efficacy and conserve the device battery life.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following particulardescription thereof, presented in conjunction with the followingdrawings wherein:

FIG. 1 shows a view of a conventional microelectrode having apermanently attached connector with the microelectrode inserted into anAdvanced Bionics® DBS lead;

FIG. 2 shows a view of the proximal end of the Advanced Bionics DBS leadand the distal end of a conventional microelectrode;

FIG. 3 shows, in accordance with the system of the present invention,the Advanced Bionics DBS lead inserted over the recording microelectrode(without a connector) of the present invention;

FIG. 4 shows, in accordance with the present invention, a view of thedistal end of multi-electrode, Advanced Bionics DBS lead and theproximal end of the microelectrode (without a connector) of the presentinvention;

FIG. 5 shows, in accordance with the present invention, a view of theproximal end of the Advanced Bionics DBS lead and the proximal end ofthe microelectrode, which is partially inserted into the lead;

FIG. 6A shows, in accordance with the present invention, a longitudinal,cross-sectional view of the microelectrode and connector having aremovable collet connection in an unlocked position;

FIG. 6B shows a cross-sectional view of the connector and microelectrodedepicted in FIG. 6A along lines 6B-6B;

FIG. 6C shows a longitudinal, cross-sectional view of the connector andmicroelectrode shown in FIG. 6A, except in a locked position;

FIG. 6D shows a cross-sectional view of the connector and microelectrodedepicted in FIG. 6C along lines 6D-6D;

FIG. 7A shows, in accordance with the present invention, a longitudinal,cross-sectional view of a connector and a microelectrode having a ballbearing connection, with the connector in an unlocked position;

FIG. 7B shows a cross-sectional view of the connector and microelectrodedepicted in FIG. 7A along lines 7B-7B;

FIG. 7C shows a longitudinal, cross-sectional view of the connector andmicroelectrode shown in FIG. 7A, with the connector in a lockedposition;

FIG. 7D shows a cross-sectional view of the connector and microelectrodedepicted in FIG. 7C along lines 7D-7D;

FIG. 8A shows, in accordance with the present invention, a longitudinal,cross-sectional view of a microelectrode and a connector having a BalSeal connection, with the connector in an unlocked position;

FIG. 8B shows a cross-sectional view of the connector and microelectrodedepicted in FIG. 8A along lines 8B-8B;

FIG. 8C shows a longitudinal, cross-sectional view of the microelectrodeand connector shown in FIG. 8A, with the connector in a locked position;

FIG. 8D shows a cross-sectional view of the connector and microelectrodedepicted in FIG. 8C along lines 8D-8D;

FIG. 9A shows a side view of a proximal end of a microelectrode 15 and aremovable connector with a threaded connection;

FIG. 9B shows a side view of the removable connector 60 andmicroelectrode 15 of FIG. 9A, with the proximal end of themicroelectrode screwed into the removable connector;

FIG. 10A shows a side view of a proximal end of a microelectrode 15 anda removable connector 60 with a set screw and a set screw hole;

FIG. 10B shows a side cross-sectional view of the removable connector 60and the microelectrode 15 of FIG. 10A with the proximal end of themicroelectrode placed into the removable connector and the set screwscrewed into place to mechanically secure the proximal end of themicroelectrode with the connector;

FIG. 11 shows a flow chart for an embodiment of a method of recordingand stimulating neural tissue;

FIG. 12 shows a flow chart for another embodiment of a method ofrecording and stimulating neural tissue;

FIG. 13 shows a flow chart for yet another embodiment of a method ofrecording and stimulating neural tissue.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

In an aspect of the present invention, a stimulation system is providedwhich includes an Advanced Bionics® DBS lead, a microelectrode and adetachable connector that can be attached to the microelectrode. Thesystem may be used together using various existing MER methods. Inaddition one or more parts of the system are compatible for use with awide variety of currently available MER recording systems.

The Advanced Bionics DBS lead has a lumen that runs axially from thedistal end to the proximal end of the lead. The microelectrode, inaccordance with the present invention, is designed without a permanentconnector. In use, the microelectrode is operated with a removable(detachable) connector which may be attached and detached to themicroelectrode at various points of a surgical procedure. Because theconnector is detachable, the microelectrode may be inserted distal endfirst into the proximal end of the lumen in the DBS lead or,alternatively, the DBS lead may be inserted distal end first over theproximal end of a microelectrode.

FIG. 1 shows a conventional recording microelectrode 10 which may beinserted into the Advanced Bionics DBS lead 40. The conventionalmicroelectrode 10 has a connector 20 which is permanently placed on theproximal end of the microelectrode. The distal end 30 of themicroelectrode 10 is uninsulated and can make electrical contact withthe surrounding tissue. The remainder of the microelectrode 10 may beinsulated, but also excluding the small portion of the proximal end ofthe microelectrode, which may be electrically connected to recordingcircuitry. The Advanced Bionics DBS lead 40 has a connector portion 41that is angled, preferably about 90 degrees from the remainder of thelead 40.

FIG. 2 shows a partial, expanded view of the conventional recordingmicroelectrode 10 inserted into the lead 40, as shown in FIG. 1. Becausethe connector 20 is permanently connected, the microelectrode can onlybe inserted distal end first into the lumen at the proximal end of theDBS lead 40, as shown in FIG. 2.

FIG. 3 shows, in accordance with the present invention, a systemcomprising a recording microelectrode 15 and an Advanced Bionics DBSstimulation lead 40 with a bent connector 41. The microelectrode 15 isshown inserted into the lumen of the Advanced Bionics DBS lead 40. Themicroelectrode does not have a fixed connector, but has both distal andproximal ends which are electrically conductive. A removable, conductiveconnector that is compatible with many currently available microdrivesmay be attached to the proximal conductive end 50 to insert themicroelectrode 15 into a target tissue such as the brain. Preferably,the remainder of the microelectrode is covered with a thin exteriorcoating of insulation, for instance, polyimide.

FIG. 4 shows a view of the distal end of the Advanced Bionics DBS lead40 and the proximal conductive end 50 of the microelectrode 15, inaccordance with the present invention. In this particular embodiment ofthe DBS lead four electrodes 45 are linearly placed in an “in-line”electrode array configuration. One of the four electrodes may be chosenas the active electrode to provide monopolar stimulation. To providebipolar stimulation, at least two of the electrodes 45 may be selected.The quadrapole electrode arrangement further facilitates stimulationflexibility once the DBS lead is chronically placed, since the bestelectrode or electrode combination may be selected for optimalstimulation. The microelectrode 15 has a conductive proximal end 50.Because the microelectrode does not have a permanent connector attachedto the proximal end 50, the microelectrode is dimensionally configuredso that it may be inserted proximal end first into the lumen opening 47at the distal tip of the DBS lead 40.

Advantageously, this allows the DBS lead to follow the microelectrode.For example, an introduction cannula may be placed into the brain. Then,using a microdrive, a microelectrode may be inserted through theintroduction cannula with or without a connector attached to themicroelectrode. Recordings are made until a suitable tissue site isfound. Once a suitable site is found, the connector is detached and aDBS lead is inserted into the introduction cannula but slipped over themicroelectrode. Once a proper position is found for the DBS lead, themicroelectrode is withdrawn and the introduction cannula is alsowithdrawn, leaving the DBS lead permanently in place.

Alternatively, the DBS lead 40 may be placed into a target tissue, forinstance the brain, followed later by the microelectrode through thelumen in the DBS lead, thereby effectively using the DBS lead as anintroduction cannula and eliminating the use of at least oneintroduction cannula.

FIG. 5 shows the Advanced Bionics DBS lead 40 advanced over themicroelectrode 15 until the proximal, connector end 50 of themicroelectrode protrudes from the proximal end of the DBS lead. Thisposition is achieved, for example, by first inserting the DBS lead 40into a target tissue, and then inserting the microelectrode into the DBSlead 40, which may be used like an introduction cannula.

FIGS. 6A, 6B, 6C, 6D, 7A, 7B, 7C, 7D, 8A, 8B, 8C and 8D depict variousviews of removable connectors having different connection mechanisms forattaching and detaching the connector 60 to the microelectrode proximalend 50.

FIG. 6A shows a longitudinal, cross-sectional view of the microelectrode15 with connector 60 in an unlocked position. The connector 60 has acollet mechanism 70 for locking the microelectrode end 50 into theconnector 60. The connector is made from a conductive material, such asa metal, which permits an extension lead linked to recording circuitryto be electrically connected to the connector and to the microelectrode.

FIG. 6B shows a cross-sectional view of the microelectrode 15 insertedwithin the connector 60 of the connector shown in FIG. 6A along thelines 6B-6B shown in FIG. 6A. FIG. 6B shows three “fingers” or segments61 at the distal end of the connector 60.

FIG. 6C shows another longitudinal, cross-sectional view of themicroelectrode 15 and connector 60 shown in FIG. 6A except that colletring 70 has been advanced forward toward the distal end 62 of theconnector 60 thereby compressing the distal end 62 of the connector. Thedistal portion 62 of the connector 60 is configured so that as thecollet 70 is advanced forward over the fingers 61, the fingers arecompressed inwards towards the connector axis.

FIG. 6D shows a cross-sectional view of the microelectrode 15 insertedinto the connector 60 along lines 6D-6D shown in FIG. 6C. The view showsthe microelectrode 15 which is compressed by three finger sections 61and thereby locking the microelectrode 15 into the connector 60. Thethree finger sections 61 are illustrative only and not limiting, as two,four or more finger sections may be used.

FIG. 7A shows a longitudinal, cross-sectional view of the microelectrode15 with connector 60 in an unlocked position. The connector 60 has twoball bearings 80 as a connection mechanism.

FIG. 7B shows a cross-sectional view of the microelectrode insertedwithin the connector 60, viewed along lines 7B-7B shown in FIG. 7A. Itcan be seen that two springs 81 are placed to compress ball bearings 80towards the center. The springs are lined up on either side of theconnector axis.

FIG. 7C shows another longitudinal, cross-sectional view of theconnector and microelectrode depicted in FIGS. 7A and 7B. In thisdepiction the microelectrode is fully inserted into the connector 60with the two ball bearings 80 compressing the proximal end 50 of themicroelectrode 15 thereby locking the microelectrode.

FIG. 7D shows a cross-sectional view of the connector 60 andmicroelectrode along lines 7D-7D shown in FIG. 7C. While the embodimentof the connector shown in FIGS. 7A, 7B, 7C and 7D show two ball bearings80 placed in opposition to each other, it is also possible to use a ballbearing connector that has only one ball bearing 80 or more than twoball bearings. Furthermore, the proximal end 50 of the microelectrode 15may have complementary surface depressions to help engage the ballbearings 80 of the connector 60 to the microelectrode.

FIG. 8A shows a longitudinal, cross-sectional view of the microelectrode15 with connector 60 having a Bal Seal connection mechanism 90 (Bal SealEngineering, Foothills Ranch, Calif.) with the connector in an unlockedposition.

FIG. 8B shows a cross-sectional view of the connector 60 and the BalSeal 90 along lines 8B-8B shown in FIG. 8A. The Bal Seal 90 is a coilthat may be under tension and formed into a ring. When the proximal endof the microelectrode 50 is inserted inside the coil ring 90, it cancompress the end of the microelectrode and lock it.

FIG. 8C shows another longitudinal, cross-sectional view of themicroelectrode and connector with the Bal Seal, as in FIG. 8A, but withthe microelectrode proximal end 50 locked into the connector with theBal Seal 90.

FIG. 8D shows a cross-sectional view of the connector 60 and thering-like Bal Seal 90 with the proximal end 50 of the microelectrodeinserted into the connector 60 and locked by the Bal Seal.

FIG. 9A shows a side view of the proximal end of the microelectrode 15with threads 101. The removable connector 60 has corresponding threads100 within the connector 60 for accepting the threads 101 on themicroelectrode.

FIG. 9B shows the microelectrode 15 and removable connector 60, as shownin FIG. 9A, but with the proximal end of the microelectrode 15 screwedinto the connector 60 with corresponding inner threads 100. Themicroelectrode can be disconnected from the removable connector 60 byturning the connector, relative to the microelectrode.

FIG. 10A shows a side view of the proximal end of a microelectrode 15and removable connector 60 having a channel 104 dimensioned to acceptthe proximal end of the microelectrode 15. In addition, the connector 60has a threaded set screw hole 103 that communicates with the channel104, which threaded set screw hole is dimensioned to accept the setscrew 102.

FIG. 10B shows a cross-sectional view of the connector 60 and proximalend of microelectrode 15, as depicted in FIG. 10A. The set screw 102 isshown inserted in the threaded set screw hole 103. By turning the setscrew in one direction, the tip of the set screw bears down mechanicallyon the proximal end of the microelectrode, thus locking themicroelectrode with the removable connector 60. The set screw can beremoved to release the microelectrode from the removable connector 60.

A collet mechanism, ball bearings and Bal Seal are only a few of thepossible types of connection mechanisms that may be used with aremovable connector. Other possible forms of connections that may beused to lock the microelectrode proximal end 50 into the connector 60include: a threaded connection, a clip connection, a set screwconnection, a spring loaded connection, a conductive adhesive connectionand an interference fit.

In an aspect of the present invention, a system for recording andstimulating neural tissue is provided which includes a microelectrode 15that can be used with a removable connector 60. In addition, themicroelectrode and removable connector may be used with a DBS leadhaving a lumen that runs axially through the entire length of the lead.When the removable connector is detached, the microelectrode 15 isdimensioned to be completely passable through the lumen of the DBS lead40. Because the connector may be removed and attached during any part ofa recording and stimulating procedure, the microelectrode can be placedinside the DBS lead commencing at either the proximal or distal lumenopenings of DBS lead 40.

As an integrated system, the DBS lead 40, the microelectrode 15 and theremovable connector 60 can operate together to flexibly allow therecording microelectrode to be placed before, after, or concurrentlywith the placement of the DBS lead. Moreover, a recording microelectrodewith a detachable connector permits the use of the Advanced Bionics DBSlead with all known MER methods and/or systems.

In another aspect of the present invention, there is provided a methodfor recording and stimulating neural tissue. In one embodiment of themethod, the microelectrode may be first implanted into a tissue site andthen followed by the DBS stimulating lead. As shown in FIG. 11, thisembodiment of the method may comprise the following steps: (a1)inserting a microelectrode into a tissue site to be recorded; (b1)attaching a removable connector to the proximal end of themicroelectrode; (c1) recording the neural tissue with themicroelectrode; (d1) repeating the previous steps (a1), (b1) and (c1)until a tissue site is confirmed which provides an acceptable neuralrecording; (e1) if a tissue site is confirmed which provides acceptableneural recording, detaching the removable connector attached to themicroelectrode; and (f1) slipping the distal end of a stimulating leadhaving a lumen over the proximal end of the microelectrode substantiallycovering the microelectrode, the lumen having a first opening at theproximal lead end and a second opening at the distal lead end. Themicroelectrode (without the connector attached) is configured anddimensioned to be completely passable through the lumen of the DBS lead,entering either at the first opening or the second opening. As analternative embodiment of the method, step (b1) may be performed beforestep (a1).

The step (b1) of attaching a removable connector may be performed byusing a connector having a connection mechanism selected from among thefollowing types of connections: a threaded connection, a clipconnection, a set screw connection, a spring loaded connection, a ballbearing connection, a Bal Seal connection, a collet connection and aninterference fit.

As another embodiment of the method, the microelectrode and DBSstimulating lead may be inserted into the tissue site together as asystem. The pre-insertion of the microelectrode into the DBS lead canbeneficially contribute to the total stiffness of themicroelectrode/stimulating lead combination and may thereby permit thecombination to be inserted into tissue more than once without incurringirreversible lead deformation.

As shown in FIG. 12, this embodiment of the method may comprise: (a2)inserting a microelectrode into a stimulating lead, wherein thestimulating lead has a lumen with a first opening at the proximal leadend and a second opening at the distal lead end and wherein themicroelectrode is configured and dimensioned to be completely passablethrough the lumen of the stimulating lead, entering either at the firstopening or the second opening; (b2) attaching a removable connector tothe distal end of the microelectrode; (c2) inserting the combination ofmicroelectrode inserted within the stimulating lead into a targettissue, (d2) recording the neural tissue with the microelectrode; (e2)repeating the previous steps (c2) and (d2) until a tissue site isconfirmed to provide an acceptable neural tissue recording; and (f2) ifa tissue site is confirmed to provide an acceptable neural tissuerecording, removing the microelectrode from the stimulating lead andleaving the stimulating lead in the target tissue. As an alternativeembodiment, the step (b2) may occur before step (a2) or, as yet anotherembodiment, step (b2) may occur after step (c2).

Again, the step (b2) of attaching a removable connector may be performedby using a connector having a connection mechanism selected from amongthe following types of connections: a threaded connection, a clipconnection, a set screw connection, a spring loaded connection, a ballbearing connection, a Bal Seal connection, a collet connection, and aninterference fit.

As a further embodiment of the method of recording and stimulatingneural tissue, as shown in FIG. 13, the microelectrode may be placedinto a DBS stimulating lead after it has been placed into the tissue.This embodiment comprises: (a3) inserting a stimulating lead into atarget tissue, which stimulating lead has a lumen having a first openingat the proximal lead end and a second opening at the distal lead end;(b3) inserting a microelectrode from its distal end, into the lumen ofthe stimulating lead at its first opening, with the microelectrodeconfigured and dimensioned to be completely passable through the lumenof the stimulating lead; (c3) attaching a removal connector to theproximal end of the microelectrode; (d3) recording the neural tissuewith the microelectrode; (e3) repeating the previous steps until a siteis confirmed to provide an acceptable recording; and (f3) if a tissuesite is confirmed to provide an acceptable recording, removing themicroelectrode from the stimulating lead.

Alternatively, in the above method, the step (c3) may occur before step(b3). In yet another alternative, the method above may include the step:stimulating the located tissue site with the stimulating lead, whichstep is performed between steps (e3) and (f3).

The step (c3) of attaching a removable connector may be accomplished byusing a connector having a connection mechanism selected from the groupconsisting of a threaded connection, a clip connection, a set screwconnection, a spring loaded connection, a ball bearing connection, a BalSeal connection, a collet connection, and an interference fit.

In operation, the system of the Advanced Bionics DBS lead,microelectrode and removable connector can be used compatibly with avariety of procedures and microdrives as provided by the specificexamples below.

Example 1 Microelectrode Placed Before the DBS Lead

An introduction cannula is inserted into the brain. The microelectrodeis inserted through the cannula with the connector attached and cellrecording is performed. When a promising tissue site is found, theconnector is detached from the microelectrode and the Advanced BionicsDBS lead is inserted over the proximal end of the microelectrode andadvanced into the brain until an electrode on the DBS lead is preciselyat the located tissue site. Macrostimulation is performed with the DBSlead. If a physiologically acceptable response is obtained, then themicroelectrode may be withdrawn and the DBS lead may be fixed forpermanent implantation. If the physiological response is not acceptable,then the DBS lead and or microelectrode can be repositioned together orseparately to locate a suitable tissue site.

Example 2 Microelectrode Placed Concurrently with DBS Lead

An introduction cannula is inserted into the brain. Themicroelectrode/Advanced Bionics DBS lead combination is inserted throughthe cannula with the connector attached to the microelectrode. Themicroelectrode is advanced slightly out of the distal end of the DBSlead and cell recording is performed. When a promising tissue site isfound, the DBS lead is advanced over the distal end of themicroelectrode until the electrodes on the DBS lead is precisely at thelocated tissue site. Macrostimulation is performed with the lead. If aphysiologically acceptable response results, then the microelectrode maybe withdrawn and the DBS lead may be fixed for permanent implantation.If the physiological response is not acceptable, then the DBS lead andor microelectrode can be repositioned such that microelectrode recordingand/or macrostimulation can be performed until the DBS lead is properlypositioned.

Example 3 Microelectrode Placed After the DBS Lead

An introduction cannula is inserted into the brain. An Advanced BionicsDBS lead has been inserted into the brain but the macrostimulation doesnot yield the desired physiological response. There is no microelectrodeinserted inside the DBS lead. A microelectrode is then inserted throughthe DBS lead, and a microrecording is performed to locate a suitabletissue site. The lead position (depth) is then adjusted to coincide withthe located site.

Example 4 “Five-At-A-Time” or Two Independent MER Microdrives

A physician using a “five-at-a-time” or two independent MER microdrivesmay perform the following procedure: conduct microelectrode recording(s)to determine the optimum target brain site based on the recordings,disconnect the removable connector from the microelectrode, insert theAdvanced Bionics DBS lead over the proximal end of the microelectrodeuntil the distal tip (electrode) of the DBS lead is over the distal endof the microelectrode, electrically connect the proximal portion of theDBS lead to stimulation circuits, conduct macrostimulation to confirmthe stimulation efficacy of the site, remove the microelectrode andsecure the DBS lead for permanent implantation. Many steps in the aboveprocedure have been omitted, including notably, the steps involvingplacement of cannulas and insertion rods before placing a microelectrodeor a DBS lead into the brain. If a DBS lead is implanted first, aseparate cannula is not required for the microelectrode since it insertsdirectly into the lumen of the DBS lead. If a microelectrode isimplanted first, the insertion cannula should be large enough toaccommodate the DBS lead which will be inserted into the cannula butslipped over the microelectrode. In either case, one cannula iseliminated with the recording and stimulation system of the presentinvention because the microelectrode is designed to be insertablethrough the lumen of the DBS lead, as compared to using at least twocannulas in the conventional procedure, one for the microelectrode andanother for the DBS lead.

Example 5 Single Tract Recording

The above-described procedure in Example 4 may be used when a singletract recording is performed. Alternatively, the method provided inExample 2 wherein the lead and recording microelectrode are insertedinto the brain as one unit may be used. During placement of the DBSlead/microelectrode unit, the distal end of the microelectrode can beslightly recessed into the distal end of the DBS lead. The DBSlead/microelectrode unit can be advanced into the brain via anintroduction cannula so that the distal tips of the lead/microelectrodeare just above the desired target site. Once the unit is placed, themicroelectrode distal tip can be extended out in small increments tomake neural recordings and to localize an optimal stimulation site. Oncethe exact site is identified, the DBS lead can be advanced to cover thelocalized site. Macrostimulation can be performed to confirm thephysiological efficacy of the site. If physiological efficacy isconfirmed, the microelectrode can be withdrawn and the DBS lead securedfor permanent implantation. If the target proves to be insufficient, theDBS lead/microelectrode can be withdrawn as a unit and reinserted as aunit into a different trajectory (tract). This procedure for electroderecording and macrostimulation is repeated until a suitablephysiological response is obtained. Once the proper site is located, themicroelectrode may be withdrawn and the DBS lead can be secured forchronic implantation.

While the microelectrode of the present invention is designed to be usedin concert with a DBS lead having an axial lumen running from end toend, the microelectrode may also be used like a conventionalmicroelectrode simply by attaching a connector.

In summary, the system of the Advanced Bionics DBS stimulating lead andmicroelectrode with a detachable connector provides the followingadvantages. The recording microelectrode is compatible with all knownMER methods, including “five-at-a-time”, two microdrives, singlemicroelectrode, and multiple insertion methods. The detachable connectorcan be configured to have the requisite electrical and mechanicalrequirements for use with various MER electrical systems and microdrivesand to be compatible with all output/inputs of known MER systems.

The stimulating/recording system of the DBS lead with a lumen extendingentirely along its length and the microelectrode without a permanentconnector attached, reduces surgical duration because it allows themicroelectrode to also function as a guide or a stylet in placing theDBS lead. Only one cannula may be needed for both the DBS lead andmicroelectrode because of the unique system arrangement in which themicroelectrode is insertable within the lumen of the DBS lead.Additionally, the microelectrode and DBS lead combination can be movedinto a tract as a unit and, thus, function as a macroelectrode/stylet,eliminating the need for inserting a separate macroelectrode.Eliminating the use of a macroelectrode obviates the need for a separateintroduction cannula for the macroelectrode. Thus, up to twointroduction cannulas may be eliminated by using the recording andstimulation system of the present invention. Elimination of two cannulasand their attendant problems of misalignment can improve placementaccuracy of the DBS lead which, in turn, may improve the therapy,prolong battery life and reduce scrapping of leads owing to missedplacements. Also, fewer cannulas reduce surgical duration and risk ofinfection because there are fewer surgical steps needed and also becausebetter accuracy of placement means fewer repeat insertions.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims. Byway of example, a DBS application has been discussed above. The leadsystem and methods described, however, may be used equally in othersites of the body other than the brain. In particular, the lead systemof the present invention can be used in any application wherein a neuralrecording is first performed to identify a tissue site to achieveoptimal neural stimulation.

What is claimed is:
 1. A system for recording and stimulating excitableneural tissue, the system comprising: a microelectrode, configured anddimensioned to be completely passable through a lumen along the axiallength of a stimulating lead, commencing from either a first opening ora second opening of the stimulating lead; and a removable connector forattaching and detaching the microelectrode from the stimulating lead,the removable connector including a locking mechanism.
 2. The system ofclaim 1, wherein the locking mechanism is selected from the groupconsisting of a threaded connection, a set screw connection, a springloaded connection, a Bal Seal connection, and a collet connection. 3.The system of claim 1, wherein the stimulation lead contains a conductorcoil-defining the lumen.
 4. The system of claim 1, wherein thestimulation lead has, as its proximal end, a connector portion that isangled from the remainder of the lead.
 5. The system of claim 1, whereinthe stimulation lead has an array of electrodes placed on the distalportion of the lead in an in-line placement.
 6. The system of claim 1,wherein the stimulation lead has an array of electrodes placed on thedistal portion of the lead in an in-line placement.
 7. The system ofclaim 1, further comprising a recorder configured for recording theneural tissue with the microelectrode.
 8. The system of claim 1, furthercomprising an insertion cannula configured for inserting themicroelectrode into the neural tissue.
 9. A system for recording andstimulating excitable neural tissue, the system comprising: astimulation lead, having a lumen along its axial length, the lumenhaving two openings, a first opening at the proximal end of the lead, asecond opening at the distal end of the lead; a microelectrode,configured and dimensioned to be completely passable through the lumenof the lead, commencing from either the first opening or the secondopening of the lead; and a removable connector attached to the distalend of the microelectrode.
 10. The system of claim 9, wherein theremovable connector includes a locking mechanism.
 11. The system ofclaim 10, wherein the locking mechanism is selected from the groupconsisting of a threaded connection, a set screw connection, a springloaded connection, a Bal Seal connection, and a collet connection. 12.The system of claim 9, wherein the stimulation lead contains a conductorcoil-defining the lumen.
 13. The system of claim 9, wherein thestimulation lead has, as its proximal end, a connector portion that isangled from the remainder of the lead.
 14. The system of claim 9,wherein the removable connector is configured to remove themicroelectrode from the stimulation lead.
 15. The system of claim 9,further comprising a recorder configured for recording the neural tissuewith the microelectrode.
 16. The system of claim 9, further comprisingan insertion cannula configured for inserting the combination ofmicroelectrode inserted within the stimulating lead into the neuraltissue.